Baryta coating of melt-coated paper



Jan. 9, 1945. H. T. GALLEY 2,366,723

, BARYTA COATING OF MELT-COATED PAPER Filed Feb. 13, 1941 SILVER HALIDE fiHOTOGRAPHIC EMULSION LAYER ADHERENT BARYTA COATING UTYRIC ACID ESTER 0F CELLULOSE HQLLIS T. GALLEY INVENTOR BYVg A T NEYS Patented Jan. 9, 1945 I UNITED STATES PATENT. OFFICE I 'BAEYTA COAT-1 55i: gg'l MELT-coATED V Hollis T. Galley, Rochester, N. Y.,

asslgnor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey '7 Claims.

This invention relates to the baryta coating of paper which has been waterproofed by coating, such as with a cellulose ester or a resin, the resulting product and the photographic paper prepared therefrom.

Recently, in many instances, it has been desirable to use paper which has been waterproofed for support for photographic emulsions. This is specially valuable in the making of photographic paper to be used for aerial mapping by photography as it permits rapid processing of the paper and the size change of the paper is minimized due to its being protected from water such as encounteredin the processing baths. One method of providing waterproofing for paper is by applying a melt-coating of a cellulose ester thereto, as described in Malm and Clarke Patent No. 2,307,783, dated January 12, 1943. Another method of waterproofing paper is to apply a cellulose ester coating thereto from a volatile solvent. Another method of waterproofing paper is to coat it with a resinous composition such as described in U. S. Patent No. 2,117,200 of B. C. Miller. This invention relates to the baryta coating of those papers containing a waterproof coating such as of a cellulose ester, which coating will adhere directly to the coating without the necessity ,of intermediate layers.

In order to make paper suitable for use for photographic paper, it is coated with a baryta composition which is ordinarily a suspension of blanc flxe or barium sulfate in a binder, usually gelatin or some other compatible material of high molecular weight such as a far-hydrolyzed cellulose ester or a synthetic resin. This coating is ordinarily applied in the form of an aqueous suspension, the coating being then dried to remove the liquid therefrom. This coating prevents infiltration from the photographic emulsion into the paper and protects the emulsion against impurities which might be contained in the paper, which would adversely affect the properties of the emulsion. The baryta coating is applied to i the paper ordinarily by means of a spreading machines.

One object or my invention is to provide a methodfor the baryta coating of paper, which contains a waterproof coating, without the necessity of applying subbin or intermediate layers to the waterproofing coating 'toenhance the adhesiveness of the baryta coating thereto. An-

: other object of myinven'tion is to provide paper,

which is readily susceptible to coating with photographic emulsions, to form a photographic paper in which the paper is protected against size change and. frilling by a cellulose ester or resin coating. Other objects of my invention will appear herein.

I have found that a very desirable water-resistant photographic paper may be made from a paper which has been previously waterproofed with a moisture-resistant, high molecular weight material such as a cellulose ester or a resin, particularly paper, which has been melt-coated on both sides therewith, which comprises first coating the paper, at least on one side, with an aqueous suspension of blanc flxe and a binder therefor also containing a limited proportion of a water-soluble liquid which is a solvent of the ester of the melt-coating and drying and then applying a compatible photosensitive emulsion thereto. I have found that the subbing of the cellulose ester coated paper prior to applying a baryta coating thereto may be dispensed with if a baryta coating composition is used which softens but does not dissolve the cellulose ester coating thereon. This is accomplished by incorporating in the baryta coating composition, which is applied to the coated paper, an organic liquid which is water-soluble and which will soften but not dissolve the cellulose ester with which the paper iscoated.

The accompanying drawing illustrates photographic paper in accordance'with my invention. This drawing shows in section the arrangementof the layers therein in which the paper is melt-coated, preferably on both sides, with a melt-coating of a butyric acid ester of cellulose for waterproofing purposes. Applied to one face of the paper and adhering to the melt-coating is a baryta coating which as described herein is caused to adhere by means of anorganic solvent which softens the surface of the melt-coating without dissolving it. Applied tofthe baryta coating is a layer of the photographic emulsion, thus forming a sensitized photographic paper in accordance with my invention.

My invention involves the application of a baryta coating to a waterproofed paper such as one melt-coated with a high molecular weight material, in which an organic solvent is present in the baryta coating compositionin s'ufiicient amountto softenthe waterproof coating on the particularly suitable for this purpose, is Carbitol paper without dissolving it away. One of the solvents, whichI have found to be acetate, also known chemically as p ethoxy-pethoxyethyi acetate. A proportion of "this organic solvent, less than 25% and more than 33 (based on the total liquid), is incorporated in a baryta coating composition to apply such a baryta. coating to a paper having thereon a waterproofing coating. If'a proportion of this solvent, as mu h as 25% or more (based on the total liquids ii. the bath), is employed, the waterproofing coating on the paper may be dissolved ofi, while with a proportion of the solvent of 3%% or less, the softening of the cellulose ester coating of the paper is not ufiicient to allow the baryta composition to adhere thereto.

Another solvent, which has been found to be exceptionally useful in the baryta coating of waterproofed paper, as referred to herein, in accordance with my invention, is Cellosolve acetate. Here again it is necessary that the amount of the solvent used be such that it will soften the cellulose ester coating on the paper but not so great that it will dissolve off that coating when the baryta is applied thereto. Other solvents, which may be employed in my baryta coating process are acetone, 1-4 dioxan, Cellosolve, methyl Cellosolve, methyl ethyl ketone and methyl acetate. Some of these solvents are very effective solvents for cellulose esters and, therefore, the limits, within which they are useful, may be even more restricted than in the case of Carbitol acetate. For instance, it is desirable to use less than of Cellosolve in a baryta coating composition when cellulose ester coatings are overcoated with baryta, the only criterion on the lower limit being that suflicient solvent is present in the baryta composition that the coating on the paper is softened enough that the baryta coating adheres thereto. In the case of some liquids which are suitable, there is the disadvantage of too low a boiling point, such as with acetone or methyl ethyl ketone. Therefore, a high concentration of acetone or methyl ethyl ketone is sometimes necessa y to preserve a baryta composition in proper physical condition over a large portion of the drying period or else drying methods must be employed which will remove the water fairly rapidly, such as by using air of particularly low humidity in the drying operation. Some solvents, such as methyl acetate, must be employed in restricted amounts when the gelatin is employed as the binder for the blanc fixe in the baryta coating composition, as gelatin will not tolerate much of some solvents. If, however, some othermaterial, which is tolerant of solvents, is employed as the binder for the blanc fixe, no such problem arises.

Paper waterproofed by melt-coating with butyric acid esters of cellulose, is particularly susceptible to baryta coating in accordance with my invention. For instance, such a melt-coated paper, is subjected to coating with a baryta composition containing blanc fixe, water and a solvent soluble in water, in accordance with'my invention, preferably with a small proportion of an organic material of high molecular weight such as gelatin or a water-susceptible cellulose ester, such as described and claimed in Fordyce Patent No. 2,129,- 052. By applying a baryta coating of this composition and carefully drying, preferably so that the ratio of solvent to water stays within the com patible range to prevent any precipitation in the composition, a paper, having a firmly-adhering baryta coating is obtained.

In the baryta coating compositions, in accordance with my invention, various-organic materials of high molecular weight which are soluble in a mixture, the greater part of the liquid of which is water, may be employed as the binder for the blanc fixe or barium sulfate therein. Gelatin has been found to be quite suitable for use for this purpose, especially where a photographic gelatin emulsion is coated thereon. The only limitation upon the use of gelatin is that it is not compatible with a liquid having too high a content of organic solvent, however, there is a satisfactory range within which it may be employed with good efiect. Another yp of material, which may be employed as the binder for the blanc fixe in a baryta coating composition, in accordance with my invention, is a watersusceptible cellulose ester, such as a cellulose acetate having an acetyl content of 20-28%. B- ters of this nature are described and claimed in Fordyce Patent No, 2,129,052. Other materials, which may be used as binders for the blanc fixe in baryta coating compositions, in accordance with my invention, are partially hydrolyzed poly. vinyl acetates or polyvinyl acetals, such as polyvinyl acetaldehyde, propionaldehyde or butyraldehyde acetals, the only criterion being that the material used as a binder fo the blanc fixe is soluble in the solvent-water combination employed. It is often desirable that the binder in the baryta composition be the same or similar to the can'ier for the silver. halide in the photographic emulsion which is to be subsequently applied. For instance, if a gelatin photographic emulsion is to be used, it is often desirable to employ gelatin as the binder in the baryta composition. In many cases, however, this is not necessary. For instance, a cellulose ester or a polyvinyl compound may be employed as the binder in the baryta composition but, nevertheless, a

gelatin photographic emulsion may be employed. If, however, a cellulose ester photographic emulsion, such as described in Salo Patent No. 2,110,491, is to be employed, it is desirable to use a like cellulose ester as the binder in the baryta composition. Also. if the carrier for the silver halide in the photographic emulsion is a polyvinyl compound, it is often desirable to employ a polyvinyl compound as the binder for the blanc fixe in the baryta composition employed.

The following examples illustrate the preparation of a baryta-coated paper in accordance with my invention:

Example I A paper, which had been melt-coated with the following composition,

Parts Low viscosity cellulose acetate butyrate 60 Dioctyl phthalate--- 30 Petrex #221 (sold by Hercules Powder Company) 10 was coated with a baryta coating having the following composition mixed together in the order given:

The baryta composition spread nicely on the melt-coated paper and upon drying was found to form a firmly-adherent layer thereon. To form a photographic paper, a photosensitive emulsion,

comprising silver halide and gelatin as the carrrer therefor, is applied to the paper on the baryta coating.

Example II A melt-coated paper was baryta coated with a baryta composition having the following composition:

A solution of water-susceptible, far-hydrolyzed cellulose acetate propionate, such as described in Fordyce Patent No, 2,129,052, one part of ester being dissolved in 11 parts of 50% Ethyl alcohol grams 735 Cellosolve cc 248 Blanc fixe A grams 570 water 54 Ethyl alrnhnl 312 This baryta composition spread well on the meltcoated paper and formed a paper which was very pliable and yet had considerable physical strength.

The baryta-coated paper thus prepared is susceptible to the applicationof a photosensitive emulsion layer, particularly where the emulsion contains a cellulose ester as the carrier for the silver halide.

Herein, wherever a melt-coated paper is referred to, it is to be understood as including processes in which a high molecular weight material is applied to the paper either in the form of a melt, such as disclosed by Miller Patent No. 2,117,200 or in which the cellulose ester or the like is first applied to the paper and then melted o having a stable coating of a high molecular weight material which renders the paper resistant to water. For example, the paper may be coated on both sides with a water-resistant cellulose derivative or with a water-resistant synthetic resin. For photographic'paper resistant to water, the use of a melt-coated paper as the base is preferred.

I claim:

1. A photographic paper which comprises a paper which has been water-proofed by applying a melt-coating thereto essentially consisting of a low viscosity cellulose acetate butyrate and a plasticizer, followed by a baryta coating from a composition essentially consisting of blanc fixe, a binder, water and an organic solvent present in sufficient amount to soften the surface of the melt-coating without dissolving it and a silver halide photographic emulsion applied directly to the baryta coating.

2. A photographic paper which comprises a paper which has been water-proofed by applying a melt-coating thereto essentially consisting of a low viscosity cellulose acetate butyrate and a plasticizer, followed by a baryta coating from a composition essentially consisting of blanc flxe, gelatin, water and an organic solvent present in sufficient amount to soften the surface of the melt-coating without dissolving it and a silver halide photographic emulsion applied directly to the baryta coating.

3. A photographic paper which comprises a paper which has been water-proofed by applying a melt-coating thereto essentially consisting of a low viscosity cellulose acetate butyrate and a plasticizer, followed by a baryta coating from a composition essentially consisting of blanciixe, a compatible cellulose ester, water and an organic solvent present in sufllcicnt amount to soften the surface of the melt coating without dissolving it and a silver halide photographic emulsion applied directly to the baryta coating.

4. A photographic paper which comprises a paper which has been water-proofed by applying a melt-coating thereto essentially consisting of a low viscosity cellulose acetate butyrate and a plasticizer, followed by a baryta coating from a composition essentially consisting of blanc flxe, a compatible synthetic resin, water, and an organic solvent present in sufiicierit amount to soften the surface of the melt coating without dissolving it and a silver-halide photographic emulsion applied directly to the baryta coating,

5. A photographic paper which comprises a paper which has been waterproofed by applying a melt-coating thereto, essentially consisting of a low viscosity butyric acid ester of cellulose and a plasticizer followed by a baryta coating from a composition essentially consisting of blanc fixe, a binder, water and an organic solvent present in sufficient amount to soften the surface of the melt-coating without dissolving it and a silver halide photographic emulsion applied directly to the baryta coating.

6. A photographic paper which comprises a paper which has been waterproofed by applying a melt-coating thereto, essentially consisting of a low viscosity cellulose acetate butyrate and a plasticizer followed by a baryta coating from a composition essentially consisting of blanc flxe, a compatible polyvinyl resin, water, and an organic solvent present in sufficient amount to soften the surface of the melt-coating without dissolving it and a silver halide photographic emulsion applied directly to the baryta coating. I

7. A photographic paper which comprises a paper which has been wate1 died by applying a melt-coating thereto, essentially consisting of a low viscosity cellulose acetate butyrate and a plasticizer, followed by a baryta coating from a composition essentially consisting of blanc flxe, a binder, water, and carbitol acetate, the latter being present in sufilcient amount to soften the surface of the melt-coating without dissolving'it and a silver halide photographic emulsion applied directly to the baryta coating.

HOLLIS T. GAILEY. 

